R-T-B-based rare earth magnet particles have excellent magnetic properties and have been extensively used in the industrial applications such as magnets for various motors employed in automobiles, etc. However, the magnet particles produced by a hydrogenation-disproportionation-desorption-recombination process (HDDR treatment) have a non-uniform decomposition structure formed by the hydrogenation/phase decomposition process and therefore exhibit a poor squareness of a demagnetization curve thereof, so that it has been difficult for the magnet particles to satisfy both an excellent residual magnetic flux density and an excellent coercive force.
In Japanese Patent Application Laid-Open (KOKAI) No. 6-128610 and Japanese Patent Application Laid-Open (KOKAI) No. 2003-301203, there is described the process for producing R-T-B-based rare earth magnet particles by HDDR treatment in which hydrogen is introduced subsequent to temperature rise step. However, since temperature control of a hydrogenation-disproportionation step (HD step) of the process is insufficient, the resulting magnet tends to exhibit a low coercive force, so that it has been difficult to obtain magnet particles capable of satisfying both an excellent residual magnetic flux density and an excellent coercive force.